1. Field of the Invention
The present invention relates generally to a recording medium containing cartridge for a recording/reproducing apparatus. Specifically, the present invention relates to a recording medium containing cartridge in which a casing is constructed so as to prevent certain problems described below.
2. Description of the Prior Art
Various types of recording medium containing cartridge are well known in the art for containing reels of magnetic tape for convenient use thereof, such as compact cassettes and microcassettes, for example. Such tape cassettes usually employ a casing comprising upper and lower halves which are mutually joined for rotatably mounting tape supply and take-up reels, holding a length of magnetic tape, therein. The casing is generally formed of synthetic resin and the halves thereof are joined by ultrasonic welding, or the like.
For example, one such conventional recording medium containing cartridge is shown in FIGS. 5 and 6. As can be seen in the drawings, the conventional recording medium containing cartridge 100 comprises an upper casing 103 and a lower casing 104. The upper casing 103 has a substantially planar upper surface 101a and a lower side wall portion 102a projecting downwardly around the periphery of the upper surface 101a. Correspondingly, the lower casing 104 has a substantially planar lower surface 101b and an upper side wall portion 102b projecting upwardly around the periphery of the lower surface 101b. The casing is formed so that the lower side wall portion 102a of the upper casing 103 mates with the upper side wall portion 102b of the lower casing 104 via abutting surfaces 107 forming the facing sides of each of the wall portions 102a and 102b. As can further be seen in FIG. 5, the abutting surface portions 107 of the upper side wall portion 102b of the lower casing 104 are provided with energy directing ribs 105 to facilitate joining of the upper and lower halves 103, 104 of the cartridge 100 by, for example, ultrasonic welding, or some similar process.
Referring to FIG. 6, a cross-sectional view of a portion of the upper and lower casings 103, 104 in a joined state is shown. As can be seen in the drawing, after joining of the upper and lower halves 103, 104 has been carried out, a burr 106 projecting inward and outwardly around the periphery of the joined upper and lower casings 103, 104, is formed. As may be seen in FIG. 6, the joined halves 103, 104 of the casing are of subtantially the same height H. The burr 106 corresponds to a center line T at the seam where the upper and lower casing halves 103, 104 are mated.
In such conventional recording medium containing cartridge casings however, drawbacks are present in that the burr 106, projects into the interior of the cartridge casing around the periphery of the casing interior, especially at corners of the casing where a substantially large burr may be formed. The burr 106 is generally located at a center line T of the casing interior, and can cause damage to the magnetic tape during winding and playing operations thereof. This in turn may cause spoilage of products during production and dissatisfaction among recording medium containing cartridge users; this is particularly true during the actual welding process when the burr is formed, as the melted resin may cause damage during production. Also, the presence of such a burr limits the amount of tape which can be accommodated by the tape reels mounted within the cartridge casing.